Effect of penicillin series antibiotics on the properties of Brucella]

Investigation of the properties of antibiotic-resistant variants obtained experimentally from various species of Brucella indicated that benzylpenicillin, ampicillin and ceporin induced significant changes in the main properties of Brucella, i.e. phagolysability, agglutinability, production of brucellacin and hydrogen sulfate, attitude to dyes. Only the nutrient requirements of Brucella did not change when it was grown on synthetic media which is of great importance for investigation of changed Brucella strains.     

Studies on the antigenic properties of serum albumins

Bovine serum albumin (BSA) is one ofthe most widely studied proteins; its structure iswell known and its antigenic properties have beendescribed in animal models. The aimof our work was to evaluate the role of conformationon antigenicity of serum albumins. This study was performed using electrophoresisassociated with the immunoblotting technique, wheresera from children allergic to BSA were used.Data obtained in this research indicatethat serum albumin antigenicity is only partiallycorrelated to its native three-dimensional structure.Heat treatment and chemical denaturation(SDS treatment) are not able to significantly decrease its capability to bind circulating IgEs. Only thereducing treatment is able to modify the antigenicityof this protein. Moreover, a direct correlationbetween the cross-reactivity observed inimmunoblotting between different serum albumins andthe percentage of their sequence identity(phylogenetic similarity of the species) was shown.     

Studies on the antigenic properties of serum albumins

Summary Bovine serum albumin (BSA) is one of the most widely studied proteins; its structure is well known and its antigenic properties have been described in animal models. The aim of our work was to evaluate the role of conformation on antigenicity of serum albumins. This study was performed using electrophoresis associated with the immunoblotting technique, where sera from children allergic to BSA were used. Data obtained in this research indicate that serum albumin antigenicity is only partially correlated to its native three-dimensional structure. Heat treatment and chemical denaturation (SDS treatment) are not able to significantly decrease its capability to bind circulating IgEs. Only the reducing treatment is able to modify the antigenicity of this protein. Moreover, a direct correlation between the cross-reactivity observed in immunoblotting between different serum albumins and the percentage of their sequence identity (phylogenetic similarity of the species) was shown.     

Factors influencing the serum levels of cholesterol and beta-lipoproteins in starving rabbits]

The influence of starvation on the lipid metabolism was studied on male rabbits under usual conditions and in the presence of pyroxidine deficiency (4-deoxypyridoxine administration) and of thiamine (oxythiamine administration), and also in administration of neurotropic preparations (phenamine, seduxen). Starvation for 7 to 10 days led to increase of cholesterol and beta-lipoproteins level in the serum. Pyridoxine deficiency and phenamine administration caused a greater increase of cholesterol and especially or beta-lipoproteins. On the other hand, thiamine deficiency and seduxen administration limited an increase of cholesterol and beta-lipoproteins during hungry stress. Administration of aerovit for prophylactic purpose promoted a decrease of the metabolic shifts. The amount of cholesterol increased in the liver of hungry animals, especially after the phenamine administration and in the presence of pyridoxine deficiency; aerovit administration prevented increased cholesterol accumulation in the liver. The differences in the cholesterol level in the serum and and the liver can be explained by the changes of its biosynthesis during hungry stress.     

The influence of the thermal factor on the antigenic properties of skin]

Results of immunochemical studies of normal and thermally-treated human skin in vitro showed at least 2 of 4-5 organospecific dermal antigens to be thermostable-they withstood heating at 100 degrees C for 3 minutes; 2 or 3 antigens were thermolabile. The thermostable antigens possessed electrophoretic migration in the field of alpha1- and gamma-globulins. The burn eschar was found to retain one of the two thermostable oranospecific antigens together with the loss of thermolabile antigen.     

Preparation and kinetic properties of immobilized benzyl penicillin acylase]

An active insoluble preparation of immobilized benzyl penicillin acylase (IBA) EC 3.5.1.11 has been obtained by its entrapping into polyacrylamide gel lattice. Due to immobilization the preparation maintains up to 87% of its initial activity. The kinetics of IBA at low substrate concentrations obeys the Michaelis-Menten law; however, the apparent KM value decreases and the temperature optimum elevates. The inhibition by the reaction products--6-aminopenicillanic acid and phenylacetic acid--has been found to be 4.3 mM. The resultant IBA preparation proves to be suitable for hydrolysis of 5% benzyl penicillin solutions.     

Effect of penicillin precursors on antibiotic biosynthesis in various strains]

The regularities of biosynthesis of 6-aminopenicillanic acid (6-APA), benzylpenicillin (BP) and phenoxymethylpenicillin (PMP) by the strains under the investigation did not significantly differ. In the absence of the precursor both the strains mainly synthesized 6-APA. Phenylacetic acid (PAA) and phenoxyacetic acid (POAA) provided directed biosynthesis: the fungus synthesized BP or PMP depending on the precursor nature. When the amount of the precursors was not sufficient, 6-APA was synthesized along with the penicillins. PAA proved to be a more active precursor than POAA. When both precursors were present in the fermentation broth, only BR was synthesized. An important distinction of strain 316A was its increased sensitivity to PAA especially in the initial period. After an increase in the PAA concentration the growth rate of strain 316A lowered to a greater extent than that of strain 284A. This was likely to determine the higher levels of penicillin production by strain 316A in the presence of POAA, a nontoxic precursor. A procedure for supplying the precursors was developed. Under the laboratory conditions it provided high levels of the penicillin production.     

Comparison of antigenic properties of the X-potato virus and its coat proteins. Effect of proteolytic cleavage on antigenic characteristics

Antigenic properties of intact potato virus X (PVX) particles and of PVX coat protein (CP) preparations were compared using different modifications of ELISA test. In the competitive ELISA test (reaction in solution) antibodies to intact virus react much stronger with PVX than with CP while antibodies to CP react much stronger with CP than with PVX. In the direct ELISA test (reaction on the solid support) the difference in reactions of antiCP antibodies with PVX and CP is eliminated while the one in reactions of antiPVX antibodies with these antigens remains. No difference was registered in reactivity of PVX absorbed directly on polystyrene or on immunoglobulin-coated wells (sandwich ELISA) to antiCP antibodies.     

Effect of the degree of cross-linking on the properties of different CLEAs of penicillin acylase

Cross-linked enzyme aggregates (CLEAs) are novel type biocatalysts well suited to catalyze reactions of organic synthesis. Penicillin acylase is a versatile enzyme that can both hydrolyze and synthesize β-lactam antibiotics. CLEAs and CLEAs covered with polyionic polymers (polyethyleneimine and dextran sulfate at two different enzyme to polymer ratios) were prepared at varying cross-linking agent to enzyme ratio: 0.15 and 0.25. Results are presented on the effect of such variables on immobilization yield, specific activity, stability and performance of penicillin acylase CLEAs in the kinetically controlled synthesis of cephalexin. The cross-linking agent to enzyme ratio had no significant effect on the specific activity of the CLEAs, but affected immobilization yield, stability in ethylene glycol medium and conversion yield and productivity in the synthesis of cephalexin, being always higher at the lower cross-linking agent to enzyme ratio. Best results were obtained with CLEAs at 0.15 glutaraldehyde to enzyme protein ratio: specific activity of hydrolysis and synthesis was 708 and 325 UI/g_CLEA respectively, conversion yield was 87%, specific productivity was 5.4 mmol cephalexin/(g_CLEA·h) and 90% of the enzyme remained active after 170 h at operating conditions.     

Effect of hemodialysis on the antioxidative properties of serum

In patients with chronic renal failure undergoing regular hemodialysis (HD), oxidative stress is involved in the development of dialysis-related pathologies. The aim of the study was to measure the effect of HD treatment on the general antioxidative status of serum with special consideration of the specific oxidizability of lipids and proteins. Indicators for the oxidative/antioxidative status of plasma were monitored at the beginning and at the end of a dialysis session on the arterial and venous side of the dialyzer. A decrease in the antioxidant status was accompanied by an increased oxidizability of proteins as well as lipids during HD treatment. During the first passage of the dialyzer, the lag time of lipid oxidation decreased from 114.0+/-19.8 to 81.5+/-18.9 min, the lag time of protein oxidation decreased from 105.0+/-24.6 to 72.9+/-21.3 min and the total antioxidative status decreased from 518+/-24 to 252+/-124 microM trolox equivalents. The carbonyl content of serum proteins was high in patients with end stage renal disease (ESRD) (3.9+/-1.1 vs. 0.9+/-0.1 nmol/mg in controls) but did not change significantly during dialysis procedure. Our data demonstrate that the susceptibility of serum lipids and proteins to oxidative modification is severely increased by HD treatment.